JPS63273616A - Production of heat-resistant methacrylic resin - Google Patents

Abstract

PURPOSE:To obtain the titled resin having excellent transparency and heat resistance, by copolymerizing methyl methacrylate with an N-substituted maleimide and aromatic vinyl compound in the presence of an inorganic salt containing monovalent cations and specific suspending and dispersing agent, such as sulfonic acid group-containing polymer. CONSTITUTION:A monomeric mixture consisting of 90-40wt.% methyl methacrylate is polymerized with 5-35wt.% N-substituted maleimide and 5-25wt.% aromatic vinyl compound is polymerized in the presence of (A) an inorganic salt as (B) two components of a water-soluble polymer consisting of 100-40wt.% monomer expressed by the formula (R is H or CH3; M is Li, K, Na or NH4), 0-60wt.% at least one of Li, Na, K and NH4 salts of (meth) acrylic acid and 0-50wt.% alkyl (meth)acrylate and (C) a water-soluble polymer consisting of 100-50wt.% at least one of Li, Na, K and NH4 salts of acrylic acid and 0-50wt.% alkyl (meth)acrylate or the component (B) as a suspending and dispersing agent to afford the aimed resin.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is directed to the production of a methacrylic resin with excellent transparency and heat resistance, which is made of a copolymer mainly containing methyl methacrylate and N-substituted maleimide. Regarding the law.

(Prior Art) Methacrylic resins containing methyl methacrylate as a main component are used for automobile parts, optical parts, etc. because of their excellent optical properties, weather resistance, and mechanical properties.

On the other hand, there are many requests for improved heat resistance, and improvements in heat resistance are expected to lead to a wider range of applications.

Many proposals have been made regarding methods for improving the heat resistance of methacrylic resins, and among them, a method of copolymerizing methyl methacrylate and N-@substituted maleimide as main monomers was disclosed in Japanese Patent Publication No. 9753/1983. ing.

The above proposal is effective in improving the heat resistance of methacrylic resin, and there are basically no restrictions on the production method, and any polymerization method such as bulk, solution, emulsion, or suspension is possible. From a production standpoint, no reliable manufacturing method has been proposed, and depending on the manufacturing method, there are problems such as the fact that the heat resistance that should originally be achieved cannot be secured due to the residual use of single groups. It is hoped that a new manufacturing method will be established. '-(Problems to be Solved by the Invention) The purpose of the present invention is to provide a highly productive method for producing methacrylic resins with excellent optical properties, mechanical properties, weather resistance, and heat resistance. .

(Means for Solving the Problems) As a result of intensive studies on the industrial production method of a copolymer consisting of methyl methacrylate, N-substituted maleimide, and an aromatic vinyl compound, the present inventors found that It has been found that industrial production is possible by a suspension polymerization method using a copolymer, and that the obtained copolymer also has satisfactory heat resistance and transparency.

That is, the present invention has 90 to 40 methyl methacrylate units.
In producing a copolymer consisting of 5 to 35% by weight of N-substituted maleimide units and 5 to 25% by weight of aromatic vinyl compound units by suspension polymerization, an inorganic salt having a monovalent cation (A > and the following suspending and dispersing agents (B) and (C)
This is a method for producing a heat-resistant methacrylic resin, characterized in that the polymerization is carried out in the presence of two components (8) or (8).

Here, the suspending and dispersing agent (B) contains 100 to 40% by weight of monohedral units represented by and at least one acrylic acid selected from lithium, sodium, potassium and ammonium salts of acrylic acid and/or methacrylic acid. 0 salt units and/or methacrylate units
It is a water-soluble polymer characterized by comprising ~60% by weight and ~50% by weight of acrylic acid alkyl ester units and/or methacrylic acid alkyl ester units having an alkyl group having 1 to 8 carbon atoms.

The suspending and dispersing agent (C) contains 100 to 50% by weight of at least one acrylate unit and/or methacrylate of lithium, sodium, potassium and ammonium salts of acrylic acid and/or methacrylic acid. It is a water-soluble polymer characterized by comprising 0 to 50% by weight of an acrylic acid alkyl ester unit and/or a methacrylic acid alkyl ester unit having an alkyl group having 1 to 8 carbon atoms.

The heat-resistant methacrylic resin obtained by the method of the present invention has a methyl methacrylate unit content of 90 to 40% by weight, more preferably 80 to 50% by weight.

If the content of methyl methacrylate units is less than 40% by weight, the mechanical strength will be significantly lowered, making it impractical.

The N-substituted maleimide unit, which is a copolymerization component used in the method of the present invention, is an essential component for improving heat resistance, and the content in the resin is 5 to 35% by weight, preferably 10 to 35% by weight.
It is 30% by weight. 5 a% N-substituted maleimide units
If it is less than 35%, the heat resistance will not be sufficiently satisfied, and if it exceeds 35[1%], the mechanical strength will decrease, which is not preferable.

As the N-substituted maleimide, N-7 enylmaleimide,
N-(2-chlorophenyl)maleimide, N-(3-chlorophenyl)maleimide, N-(4-chlorophenyl)maleimide, N-(2゜4.6-dolichlorophenyl)maleimide, N-(4-bromophenyl) Maleimide, N-(2゜4.6-dribromophenyl)maleimide, N-(2-methylphenyl)maleimide, N-(4-
methylphenyl)maleimide, N-(2,6-dimethylphenyl)maleimide, N-(2-t-butylphenyl)maleimide, N-cyclohexylmaleimide, N-methylmaleimide, N-ethylmaleimide, N-n-butyl maleimide, N-tert-butylmaleimide, N-
Examples include laurylmaleimide.

The aromatic vinyl compound unit, which is another copolymerization component used in the method of the present invention, mainly plays an auxiliary role in increasing the copolymerizability of the N-substituted maleimide and improving the heat resistance. The content of 8 in it is 5 to 25% by weight, more preferably 7 to 20% by weight. If the aromatic vinyl compound unit is less than 5% by weight, the N-substituted maleimide remains in the resin as a single substance, making it difficult to obtain the heat resistance inherent to I#4 resin.
Moreover, if it exceeds 25% by weight, the optical properties of the methacrylic resin deteriorate, which is not preferable.

Examples of such aromatic vinyl compounds include styrene, p-methylstyrene, α-methylstyrene, and halogenated styrenes such as p-chlorostyrene and p-bromostyrene.

In producing the above-mentioned copolymer by suspension polymerization, the present invention uses two components of affi (A) having a monovalent cation and suspension dispersants (B) and (C), or (B). This makes polymerization possible for the first time, and the resulting copolymer also has satisfactory heat resistance.

The inorganic salt (A) having a monovalent cation used in the method of the present invention is, for example, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, carbonic acid,
Examples include sodium, potassium, and ammonium salts of boric acid, citric acid, acetic acid, lactic acid, and tartaric acid. (A)
The addition ratio is 0.01 to 2 parts, preferably 0.05 to 1 part by weight per 1 part by weight of water. 0.0
If the amount is less than 1 part by weight, the shape and size of the resulting beads may become non-uniform, or the 11 particles may coalesce, which is not preferable.

Moreover, if it exceeds 2 parts by weight, it will have an undesirable effect on the optical properties of the copolymer.

The suspending and dispersing agent (B) contains 100 to 40% by weight of the single unit represented by and at least one acrylic 111 salt unit selected from lithium, sodium, potassium, and ammonium salts of acrylic acid and/or methacrylic acid, and/or Or methacrylic acid f!
A water-soluble polymer characterized by comprising 0 to 60% by weight of A111 position and 0 to 50% by weight of acrylic acid alkyl ester units and/or methacrylic acid alkyl ester units having an alkyl group having 1 to 8 carbon atoms. . The addition ratio of (B) is 0.001 to 1 part by weight, preferably 0.005 to 0.5 part by weight per 100 parts by weight of water.

If the weight is less than 0.001, the beads may become uneven.
It is not desirable because it leads to unification. Further, even if the amount exceeds one layer, it does not affect bead formation, but it is not preferable because it tends to cause collection of the polymerization system or is included in the copolymer and causes fish eyes.

The suspending and dispersing agent (C) contains at least one acrylate unit and/or methacrylic [X] ¥i position 100 to 50% by weight of lithium, sodium, potassium, and ammonium salts of acrylic acid and/or methacrylic acid. % and acrylic acid alkyl ester units having an alkyl group having 1 to 8 carbon atoms and/or methacrylic acid alkyl Nisder units O to 50% by weight. The addition ratio of (C) is water'10011
0 to 1 part by weight, more preferably 0.003 to 1 part by weight
It is 0.5 part by weight. Although (C) does not pose a problem in the stability of bead production even if it is not used in combination, it is preferable to use it in combination in order to make the beads uniform. Although there is no Weg for bead formation even if the concentration exceeds one helical part, the polymerization system becomes more foamy,
It is undesirable because it is included in the copolymer and tends to cause fish eyes. Although it is possible to produce beads using only the two components (A> and (C)), it is not preferable from the standpoint of polymerization stability, such as the inclusion of irregularly shaped beads and the formation of polymers adhering to the walls of the polymerization tank and stirring blades.

The suspension polymerization of the present invention is carried out by a known method under stirring for 50 to 15 hours.
Polymerization can be carried out at a polymerization temperature of 0° C. for a predetermined period of time.

In addition, the weight pressure of the monomer phase and the aqueous phase during suspension polymerization is monomer phase/aqueous phase = 1/10 to 1/1, but from the viewpoint of productivity it is 1/3 to 1/1. is preferred.

The polymerization initiator that can be used in the present invention is not particularly limited as long as it is a radical polymerization initiator that is soluble in the monomer.
For example, 2.2'-azobisisobutyronitrile, 2.2
Azo initiators such as '-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2'-azobisisobutyrate, lauroyl peroxide, penzoyl peroxide, t-butylperoxyisobutyrate, Examples include peroxides such as acetyl peroxide.

Further, the main purpose of the resin of the present invention is to use it as a molding material, and it is preferable to use a chain transfer agent to adjust the degree of polymerization of the copolymer. As additives used for this purpose, n-butyl mercaptan, n-butyl mercaptan, Examples include mercaptans such as n-octylmerh-butane and n-dodecylmercaptan, thioglycolic acid and thioglycolic acid esters.

The copolymer beads obtained by the production method of the present invention can be pelletized using a vented extruder or the like by a known method and then injection molded.

Furthermore, in the resin of the present invention, lubricants, dyes and pigments, ultraviolet absorbers, heat stabilizers, etc. may be added as necessary during polymerization or pelletization.

(Example) The following abbreviations were used for monomers, inorganic salts (A), and suspending and dispersing agents in Examples. Methyl methacrylate (MMA)
, N-7 enylmaleimide (PI), N-(2-chlorophenyl)maleimide CC, PI), N-(2-methylphenyl)maleimide (MPI), N-cyclohexylmaleimide (CHI), N-(2 , 6-dinitylphenyl)maleimide (EPI), styrene (ST), α-methylstyrene (MST), g! Sodium dihydrogen tetraate (
A-1>, g4(dis)sodium hydrogenate (A-2), sodium sulfate (A-3), carboxymethyl cellulose (CMC).

The heat distortion temperature in the examples is a value measured according to ASTM D648.

Further, suspension dispersants (B) and (C) used in Examples were manufactured as follows.

(B-1> Sodium styrene p-sulfonate 150g
, 600 g of ion-exchanged water was charged into a separable flask No. 21, and the temperature was raised to 60° C. with stirring under an N2 atmosphere.
Add 0.2 g of ammonium persulfate and hold for 3 hours,
Then, it was kept at 70°C for 2 hours and then cooled to 240 pois.
A colorless and transparent solution of (25° C.) was obtained.

(B-2) Sodium styrene p-sulfonate 100g
, 209 sodium methacrylate, 30 g of methyl methacrylate, and 600 g of ion-exchanged water were placed in a separable flask No. 21, and the temperature was raised to 60°C with stirring under N2 atmosphere, and then 0.2 g of ammonium persulfate was added and maintained for 3 hours. Then, it was kept at 70°C for 3 hours and then cooled to 370p.
A colorless and transparent solution of oise (25°C) was obtained.

(C-1> Potassium hydroxide 112g, ion exchange water 30g
0g was placed in a 21 separable flask, heated to 50°C with stirring under N2 atmosphere, and methyl methacrylate 2
Add 00g. The internal temperature rises due to saponification heat generation, and 7
After holding at 0°C for 1.5 hours, the temperature was lowered to 60°C, and 0.29% of ammonium persulfate was added, and after 5 hours, 50% of ion-exchanged water was added.
Add 0g to dilute, 21 poise (25℃)
A cloudy solution was obtained.

(C-2) 580 g of ion-exchanged water was placed in a 21 separable flask, heated to 80°C with stirring, and 20 g of a finely powdered polymer consisting of 70% by weight of methacrylic acid units and 30% by weight of methyl methacrylate units was added. to disperse,
Then, 6.5 g of sodium hydroxide dissolved in 20 g of ion-exchanged water is added. After 2 hours, cool and 2 poise
A colorless and transparent solution (25° C.) was obtained.

Example 1 A monohung body consisting of 70 parts by weight of methyl methacrylate, 20 parts by weight of N-(2-O-lophenyl)maleimide, 10 parts by weight of styrene, 0.3 parts by weight of lauroyl peroxide, and parts by weight of n-octyl mercaptan. 20kg of solution and 10kg of ion exchange water
0 parts by weight, 0.2 parts of sodium dihydrogen phosphate, 0.21 ff 1 part of sodium (di) hydrogen phosphate, (B-1)
50 kg of an aqueous solution consisting of 0.1 interspace and 0.05 part by weight of (C-1) was charged into a jacketed 1001 pressure-resistant polymerization tank, stirred under N2 atmosphere, and heated at a polymerization temperature of 80°C by passing warm water through the jacket. started. Two hours after the start of polymerization, the polymerization tank was sealed, steam was passed through the jacket, the temperature was raised to 120°C, and the temperature was maintained for another two hours to complete the polymerization.

The polymerization system does not foam, is very stable, and has an average particle size of 0.
．． Uniform beads of 32 am were obtained in good yield, and the polymer adhering to the walls of the polymerization tank or stirring blades was free of problems. After washing and drying the beads, they were pelletized at 250°C using a 60Mφ vented extruder, and then molded into physical property test pieces using an injection molding machine at 250°C. As a result, the heat distortion temperature was 118°C, and the molded product It was transparent with a very slight yellow tinge, and there were no external defects such as fish eyes or silver.

Examples 2 to 8, Comparative Examples 1 to 5 Table 1 shows the results of the production method according to Example 1 while varying the monomer solution composition and aqueous solution composition.

Inorganic salt (A), suspending and dispersing agent (8) and (C
) is the ratio to 10,000 weight of water, and the weight ratio of the monomer phase to the aqueous phase is all monomer phase / water phase including comparative examples.
Water phase = 1/2.

Furthermore, the obtained beads were evaluated in the same manner as in Example 1.

(Effects of the Invention) According to the method of the present invention, the polymerization reaction is extremely stable, beads with uniform particle diameters are obtained, and almost no polymer adhesion to the walls of the polymerization tank or stirring blades is observed. In addition, the obtained resin has excellent heat resistance, transparency, and moldability, and can be used in fields where acrylic resins have traditionally been used, as well as in fields that require particularly high heat resistance. Therefore, it is expected to be used in a wide range of applications that could not be used with conventional methacrylic resins.

Claims (1)

[Claims] (1) Methyl methacrylate unit 90-40% by weight, N-
In producing a copolymer consisting of 5 to 35% by weight of substituted maleimide units and 5 to 25% by weight of aromatic vinyl compound units by suspension polymerization, an inorganic salt having a monovalent cation (A
) and the following suspending and dispersing agents (B) and (C), or a method for producing a heat-resistant methacrylic resin, which comprises polymerizing in the presence of (B). Here, the suspending and dispersing agent (B) has a general formula ▲ mathematical formula, chemical formula, table, etc. ▼ [However,;
, m, and p; ;R is H or CH_3; ;M is Li, Na, K, or NH_4; ] 100 to 40% by weight of the monomer units represented by and at least one acrylate unit and/or methacrylate unit of lithium, sodium, potassium and ammonium salts of acrylic acid and/or methacrylic acid
It is a water-soluble polymer characterized by consisting of ~60% by weight and 0~50% by weight of acrylic acid alkyl ester units and/or methacrylic acid alkyl ester units having an alkyl group having 1 to 8 carbon atoms. The suspending and dispersing agent (C) contains 100 to 50% by weight of at least one acrylate unit and/or methacrylate unit among lithium, sodium, potassium and ammonium salts of acrylic acid and/or methacrylic acid and carbon. It is a water-soluble polymer characterized by comprising 0 to 50% by weight of acrylic acid alkyl ester units and/or methacrylic acid alkyl ester units having 1 to 8 alkyl groups.